A lithographic apparatus is a machine that applies a desired pattern onto a substrate, usually onto a target portion of the substrate. A lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). In that instance, a patterning device, which is alternatively referred to as a mask or a reticle, may be used to generate a circuit pattern to be formed on an individual layer of the IC. This pattern can be transferred onto a target portion (e.g. comprising part of, one, or several dies) of a substrate (e.g. a silicon wafer). Transfer of the pattern is typically via imaging onto a layer of radiation-sensitive material (resist) provided on the substrate. In general, a single substrate will contain a network of adjacent target portions that are successively patterned. Known lithographic apparatus include so-called steppers, in which each target portion is irradiated by exposing an entire pattern onto the target portion at one time, and so-called scanners, in which each target portion is irradiated by scanning the pattern through a radiation beam in a given direction (the “scanning”-direction), while synchronously scanning the substrate parallel or anti-parallel to this direction. It is also possible to transfer the pattern from the patterning device to the substrate by imprinting the pattern onto the substrate.
K. Ota, e.a., New Alignment Sensors for Wafer Stepper, SPIE, Vol. 1463, Optical/Laser Microlithography IV (1991), p. 304-314, and N. R. Farrar, e.a., Performance of through-the-lens/off-axis laser alignment systems and alignment algorithms on Nikon wafer steppers, SPIE Vol. 1673, Integrated Circuit Metrology, Inspection, and Process Control VI (1992), p. 369-380, disclose a laser step alignment (LSA) arrangement. In such a laser step alignment arrangement marks are used, including a plurality of square shaped structures arranged in rows and columns. A laser produces an elongated alignment measurement spot on the square shaped structures in a column. The incoming alignment beam is diffracted by the mark and a number of diffraction orders are generated and transmitted back to a detector. The zero-th diffraction order may be blocked before it hits the detector. The detector may generate a detector signal for a processor that determines the location of the mark column irradiated with the spot. By directing the spot to all columns consecutively and measuring the location of all columns in this way, the measured locations of the columns can be averaged and the location of the mark may be determined.
In this set-up, one such mark is used to measure a position of the mark in a first direction. To measure a position in another, second direction, e.g., perpendicular to the first direction, a further mark is provided that is scanned in the second direction. In general, marks may be provided in scribelanes on a substrate, extending in a x-direction and marks in scribelanes extending in an y-direction. Thus, to perform an alignment measurement in the x-direction and in the y-direction, the marks in the x-scribelanes and the y-scribelanes should be moved such that they may be measured consecutively by the alignment measurement arrangement used. However, such movement cost time. Moreover, these marks occupy costly space in the scribelanes which may be also used for all kinds of electrical test circuits.